Stock filter on the HPI Baja 5b This is not a standard scooter type pre-filter, this is made to the dimensions of your HPI stock pre-filter. Keep unwanted dirt, water and sand away from your stock filter all while creating a killer look with some extra color. Your stock filter will last longer and you will have to clean it less often when using this pre-filter. They are washable and reusable and simple to install. Choose your color.